1. Field of the Invention
The present invention relates to a pressure-pulse-wave detecting apparatus which includes a pressure-pulse-wave sensor adapted to be pressed against an artery of a living subject via a skin of the subject.
2. Related Art Statement
In some cases, it is needed to detect a pulse wave from a large-diameter artery of a patient, such as a carotid artery or a brachial artery, so as to monitor a dynamic circulatory condition of the patient and thereby make a diagnosis thereon. In those cases, a pressure-pulse-wave detecting apparatus is widely used which presses the artery via the skin and detects a pressure pulse wave, i.e., a pressure oscillation that is produced by the artery and is propagated to the skin. Since the pressure-pulse-wave detecting apparatus can non-invasively detect the pulse wave, it can reduce the discomfort the patient feels.
When the pressure-pulse-wave detecting apparatus is used to detect the pressure pulse wave, it is needed to press a portion of the artery to some degree. However, that portion of the artery may suffer stenosis or arteriostenosis because of, e.g., arteriosclerosis. If the portion of the artery that suffers arteriostenosis and accordingly cannot allow a normal flow of blood, is pressed by the apparatus, the flow of blood is more strongly blocked to disadvantage. Meanwhile, in the case where a portion of an artery that suffers stenosis because of sclerosing plaque, is pressed, the plaque may be broken, and blood clots may outflow and generate thrombus on the downstream side. Thus, it is needed to detect a pressure pulse wave from a portion of an artery that is free of stenosis. However, the conventional pressure-pulse-wave detecting apparatus cannot judge whether an artery suffers stenosis or not.
It is therefore an object of the present invention to provide a pressure-pulse-wave detecting apparatus which makes it possible to judge whether a portion of an artery from which a pressure pulse wave is to be detected thereby suffers stenosis.
The Inventor has carried out extensive studies to achieve the above object and found that an artery which suffers stenosis causes a turbulent flow of blood and a pressure-pulse-wave signal obtained from the artery contains a signal component (hereinafter, referred to as the xe2x80x9cblood-flow-noise signalxe2x80x9d) having frequencies characteristic of the turbulent flow. Therefore, if the blood-flow-noise signal is extracted from the pressure-pulse-wave signal, it is possible to judge, from a magnitude of the blood-flow-noise signal, whether a portion of an artery from which a pressure pulse wave is to be detected suffers stenosis. The present invention has been developed based on this finding.
The above object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for detecting a pressure pulse wave produced by an artery of a living subject, comprising a pressure-pulse-wave sensor which is adapted to be pressed against the artery of the subject via a skin of the subject, detects the pressure pulse wave produced by the artery, and generates a pressure-pulse-wave signal representing the detected pressure pulse wave; a band-pass filter which extracts, from the pressure-pulse-wave signal, a blood-flow-noise signal having frequencies in a prescribed blood-flow-noise frequency range; and an output device which outputs the blood-flow-noise signal extracted by the band-pass filter.
According to this aspect, the band-pass filter extracts, from the pressure-pulse-wave signal, the blood-flow-noise signal, and the output device outputs the blood-flow-noise signal. Therefore, an operator such as a doctor or a nurse can judge, from a magnitude of the blood-flow-noise signal given by the output device, whether a portion of the artery that is pressed by the apparatus suffers stenosis.
According to a second aspect of the present invention, there is provided an apparatus for detecting a pressure pulse wave produced by an artery of a living subject, comprising a pressure-pulse-wave sensor which is adapted to be pressed against the artery of the subject via a skin of the subject, detects the pressure pulse wave produced by the artery, and generates a pressure-pulse-wave signal representing the detected pressure pulse wave; a band-pass filter which extracts, from the pressure-pulse-wave signal, a blood-flow-noise signal having frequencies in a prescribed blood-flow-noise frequency range; a blood-flow-noise-information obtaining means for obtaining blood-flow-noise information representing a magnitude of the blood-flow-noise signal extracted by the band-pass filter; and an output device which outputs the blood-flow-noise information obtained by the blood-flow-noise-information obtaining means.
According to this aspect, the band-pass filter extracts, from the pressure-pulse-wave signal, the blood-flow-noise signal, the blood-flow-noise-information obtaining means obtains blood-flow-noise information representing a magnitude of the blood-flow-noise signal, and the output device outputs the blood-flow-noise information. Therefore, the operator can judge, from the magnitude represented by the blood-flow-noise information, whether a portion of the artery that is pressed by the apparatus suffers stenosis.
According to a third aspect of the present invention, there is provided an apparatus for detecting a pressure pulse wave produced by an artery of a living subject, comprising a pressure-pulse-wave sensor which is adapted to be pressed against the artery of the subject via a skin of the subject, detects the pressure pulse wave produced by the artery, and generates a pressure-pulse-wave signal representing the detected pressure pulse wave; a band-pass filter which extracts, from the pressure-pulse-wave signal, a blood-flow-noise signal having frequencies in a prescribed blood-flow-noise frequency range; a stenosis judging means for making, based on a magnitude of the blood-flow-noise signal extracted by the band-pass filter, a judgment about whether a portion of the artery that is pressed by the pressure-pulse-wave sensor suffers stenosis; and an output device which outputs the judgment made by the stenosis judging means.
According to this aspect, the band-pass filter extracts, from the pressure-pulse-wave signal, the blood-flow-noise signal, the stenosis judging means makes, based on the magnitude of the blood-flow-noise signal, the judgment about whether the portion of the artery that is pressed by the apparatus suffers stenosis, and the output device outputs the judgment. Therefore, the operator can easily know about whether the portion of the artery that is pressed by the apparatus suffers stenosis.